Neurological disorders are often caused by neural impulses failing to reach their natural destination in otherwise functional body systems. Local nerves and muscles may function, but, for various reasons, such as injury, stroke, or other cause, the stimulating nerve signals do not reach their natural destination. For example, paraplegic and quadriplegic animals have intact nerves connected to functioning muscles and only lack the brain-to-nerve link. Electrically stimulating the nerve or muscle can provide a useful muscle contraction.
Further, implanted devices may be sensors as well as stimulators. In either case, difficulties arise both in providing suitable, operable stimulators or sensors which are small in size and in passing sufficient energy and control information to or from the device, with or without direct connection, to satisfactorily operate them. Miniature monitoring and/or stimulating devices for implantation in a living body are disclosed by Schulman, et al. (U.S. Pat. No. 6,164,284), Schulman, et al. (U.S. Pat. No. 6,185,452), and Schulman, et al. (U.S. Pat. No. 6,208,894).
It must be assured that the electrical current flow does not damage the intermediate body cells or cause undesired stimulation. Anodic or cathodic deterioration of the stimulating electrodes must not occur.
In addition, at least one small stimulator or sensor disposed at various locations within the body may send or receive signals via electrical wires.
The implanted unit must be sealed to protect the internal components from the body's aggressive environment. If wires are attached to the stimulator, then these wires and the area of attachment must be electrically insulated to prevent undesired electric signals from passing to surrounding tissue.
Miniature stimulators offer the benefit of being locatable at a site within the body where a larger stimulator cannot be placed because of its size. The miniature stimulator may be placed into the body by injection. The miniature stimulator offers other improvements over larger stimulators in that they may be placed in the body with little or no negative cosmetic effect. There may be locations where these miniature devices do not fit for which it is desired to send or receive signals. Such locations include, but are not limited to, the tip of a finger for detection of a stimulating signal or near an eyelid for stimulating blinking. In such locations, the stimulator and its associated electronics are preferably located at a distance removed from the sensing or stimulating site within the body; thus creating the need to carry electrical signals from the detection or stimulation site to the remote miniature stimulator, where the signal wire must be securely fastened to the stimulator.
Further, the miniature stimulator may contain a power supply that requires periodic charging or require replacement, such as a battery. When this is the case, the actual stimulation or detection site may be located remotely from the stimulator and may be located within the body, but removed a significant distance from the skin surface. By having the ability to locate the miniature stimulator near the skin while the stimulation site is at some distance removed from the skin, the miniature stimulator and its associated electronics can be more effectively replaced by a surgical technique or more efficiently recharged through the skin by any of several known techniques, including the use of alternating magnetic fields. If the electronics package is replaced surgically, then it is highly desirable to have the capability to reconnect the lead wires to the miniature stimulator via an easy, rapid and reliable method, as disclosed herein.